Rainforest in the Amazon region of Brazil
Photo: Paulo Lopes / ZUMA Wire / imago images
Forests play an important role in the fight against global warming.
They are seen as a buffer against climate change because they store large amounts of the greenhouse gas CO₂.
However, the balance in favor of climate protection only works out if more greenhouse gas is stored through tree growth than released through forest that has disappeared.
Ironically, this becomes a problem with the Amazon rainforest, the largest forest area on earth at 5.5 million square kilometers. In the past ten years, around 20 percent more CO₂ has been released into the atmosphere from the green spaces in South America, most of which are on the territory of Brazil, than could be absorbed. This is what researchers working with Yuanwei Qin from the University of Oklahoma report in a study published in the journal Nature Climate Change. For their work, the researchers created a climate footprint for the rainforest in Brazil.
According to their calculations, the plants in the Amazon basin absorbed around 13.9 billion tons of CO₂ between 2010 and 2019. But 16.6 billion tons were sold. The numbers showed for the first time that the Brazilian Amazon rainforest had tilted, according to co-author Jean-Pierre Wigneron from the French National Institute for Agronomic Research (Inra). “He's a net issuer now. We don't know at what point this change could become irreversible, ”Wigneron told the AFP news agency.
Usually the forest is in a natural cycle: old trees die, new ones are added. But the researchers recorded more and more human interventions that disrupt this natural cycle. It is not just about the pure destruction of the forest through deforestation or slash and burn, but also about factors that initially contribute to a weakening of the forest substance and have more long-term consequences.
This so-called forest degradation is caused, for example, by the fact that trees on the edge of deforested areas are more susceptible. Or the consequences of droughts, which put pressure on branches and leaves, increasing tree mortality in the long term and negatively affecting the ability to absorb carbon. While deforestation is relatively easy to see through satellite imagery, many other types of forest degradation are much more difficult to track. But for this, too, the researchers evaluated data from satellite images in the study.
They conclude that the effects of forest degradation on the climate are now more serious than those caused by deforestation alone. However, it continues to progress at a terrifying pace. "We found that the loss of forest land in 2019 was greater than in 2015 - possibly due to the recent relaxation of forest protection policy," the researchers wrote. The extent of deforestation increased almost fourfold during the observation period. From around one million hectares to 3.9 million, an area the size of the Netherlands.
Ultimately, the increasing destruction of the forest is mainly due to slash and burn and deforestation. Politicians in Brazil are also to blame for this. Because in his term of office, which began in January 2019, President Jair Bolsonaro relaxed environmental protection measures. That is why more areas were cleared for agriculture, cattle breeding or other economic use, as satellite evaluations have shown.
Healthy ecosystems make a significant contribution to combating climate change.
In the past 50 years, plants and soils have absorbed around 30 percent of CO₂ emissions, the oceans more than 20 percent.
But scientists have been observing for a long time that forests are becoming ever smaller carbon stores.
According to a study from last year, primeval forests in South America and Africa absorb up to 30 percent less CO₂ than they did in the 1990s.
Already in this study the researchers warned: If the trend continues, rainforests could develop from a CO₂ reducer to a CO2 emitter in the next 15 years.